Piston skirt expander



April 24, 1945.

- M. E. SIPE PISTON SKIRT EXPANDER Filed July 24, 1944 INVENTOR.

MARTIN EQSIPE oil will result.

Patented Apr. 24, 1945 UNITED STATES PATENT OFFICE PISTON SKIRT EXPANDER Martin EdSipe, Denver, Colo.

Application July 24, 1944, Serial No. 546,302 3Claims. (01. 309- 12) This invention relates to improvements in means for expanding a split skirt pistonto eliminate piston slapf excessive oil consumption and blow-by and. also to distort solid trunk pistons.

Pistons for use in high speed internal combustion engines are commonly made from aluminum alloy. Such pistons are usually formed with a head and a skirt, the latter being partially separatedfrom the head bycircumferential grooves.

The skirt is usually slotted longitudinally so. that it; will. yield to pressure and is initially of a diameter that it will be inclose contact with the slapi blow-by and undue leakage of gas and.

To remedy the above defects, it is customary V to provide resilient means for expanding or distorting the piston to maintain its outside diameter constant, or in other words to compensate for wear and collapse.

It is the principal object of this invention to that they can be readily assembled into units of l A further object i to provide 'an expander that ified form'of the invention applied to a solid trunk piston; and

Figure '7 is a fragmentary topplan view of the expander shown in Figure 6. t

In the drawing reference numeral Ill designates the head of the piston and this is provided with piston ring grooves Il. Positioned below the head is a skirt I2 that is partially separatedfrom the head by means of one or more cylindrical cuts" or grooves I3. The skirt is sometimes divided by means of a vertical cut l4. so that it may.

be expanded. Each cylinder is provided with pin bosses 15 through which the piston pin l6 extends. The expanding device is formed. from two identical pieces of spring steel; which have been designated in their entirety by reference numeral ll. Each of the expander members has a substantially straight portion at and concave end portions b. End. portions are splitforming central tongues l8 and Island spring. fingers 20'. The spring fingers are reversely bent. as indicated by reference numeral 2|. The tongue I8 is curved in the manner shown. in Figure 4 and the tongue I9 is similarly curved, and is provided with. laterally extending portions 22. that can be folded over the tongue l8 of the other member in the manner shown in Figure 2. Each ofthe expander members is provided with a hole 23 for the recan be compressed and held in this condition for insertion in the piston and. which can be easily and quickly released after positioned.

The above and other objects that may'become apparent as this description proceeds are attained by means of a construction and arrangement of parts that will'now be described in detail, reference for-this purpose being had to the accompanying drawing in which the invention ha been illustrated, and in which:

Figure 1 is a section taken on line l-ljFigure 2;

Figure 2 is a partial section taken on Figure 1;

Figure 3 is an end elevation of the expander looking in the direction of arrows3-3, Figure 1;

Figure 4 is a top plan view of one of the expander parts showing the same held in compressed position;

Figure 5 is a side elevation of the part shown in Figure 4;

Figure 6 is a fragmentary section similar to that shown in Figure 2 and shows a slightly modline 2-2,

ception of the pistonpin and is normally of such length that it cannot be inserted into the interior of the piston without first compressing it; Before explaining how the parts are. compressed and held in compressed. position, the manner of asof these membersare assemblediinto the position shown in Figure 1; The ends of tongues l8 are positioned between the projections 22 and the latter arefolded into the position shown in Figure 2. After this has been done, the two parts may be spotwelded or may be riveted in position, if

this should be deemed necessary. In the assembly illustrated it is assumed that the parts have been spotwelded at the point designated by reference numeral 24. After the expander has been assembled into the position shown in Figure 1, it is placed in a vice or other compressing device and reduced in length from the dotted line position to the full line position shown in Figures pander has been compressed, a steel wire 26 is attached in the manner shown. This wire has its ends provided with lateral portions 21 that project through the holes 25 and hold the parts in compressed condition. For eachexpander there are four steel wires or links 26 for each complete assembly. When the expander is to be inserted into the piston, the piston pin is first removed and. the expander inserted into theopen end of the skirt with openings 23 in alignment with the openings in pin bosses l5. After the piston pin and connecting rod have been inserted, the workman, by means of a suitable tool, releases one end of each of the links 26, thereby permitting the expander to increase in length and to engage the inner surface of the skirt in the manner shown in Figure 1. The length of the parts from which the expander is constructed is so designed that the force exerted on the skirts will tend to move them outwardly with a sulficient force to maintain them in proper pressure relation with the inner wall of the cylinder and to keep them in sealing contact therewith so as to compensate for wear.

. Particular attention is called to the specific construction of the expander elements and to the fact that they are duplicates which simplifies the manufacture as only a single set of dies is necessary for the production of the two parts.

Another feature of importance is the manner in which the expander is held in compressed relation. It will be observed that the compression takes place in the direction of the length of the expander and owing to this feature the two reversely bent portions at each end can be spaced from each other in the manner indicated at 28 in Figure '1.

Instead of splitting the skirt as shown in Figures 1 and 2, it is sometimes made continuous and of somewhat thinner material as shown in Figure 6. In solid trunk pistons the skirt, instead of being perfectly circular is slightly oval. Regardless of whether the skirt is circular or not to begin with, the expander will distort it slightly because it is quite thin. The distorting action of the expanderkeeps the skirt in contact with the cylinder walls at all times, regardless of wear.

In Figure 6 the expander has been shown slightly modified, as it is desirable to exert the expanding or distorting force nearer the botton of 'the skirt, The two spring fingers b at each end have been combined into a single one of approximately the combined width of the two shown in the other modification. The tongues.

l8 and [9 are at the top. In other particulars the expander is the same as the one described and functions in the same manner.

In Figure 7 a fragmentary top plan view has been shown of the modified construction shown in Figure 6. Since the modified form merely omits the upper curved end portions b the only difierence between the appearance from Figure 1 is that the outer lines of l8 and I9 extend across the two lines. representing the thickness. The

curved ends 2! are provided with openings 25.

for the reception of the hooked ends of the wires 26 which holds the parts in contracted position to facilitate placing the expander within the piston in the manner shown more clearly in Figures 4 and 5.

Having described the invention what is claimed as new is:

1. A piston skirt expander which comprises a pair of reversely arranged bowed strips of spring metal forming an assembly of oval shape, the ends of the members being separated into at least two parts by notches, one portion forming a curved inwardly extending tongue positioned to lap the corresponding tongue on the opposed part to interconnect the two parts, the portions adjacent the tongues having their extreme ends curved rearwardly, for contacting the inner surface of a piston skirt, the extreme ends of the reversely bent portions having opening for the reception of tension members for holding the expander in contracted position.

2. A piston skirt expander, of generally oblong shape, formed of spring metal and adapted to be inserted into the skirt of a piston and having end portions adapted to engage with the inner surface of the skirt, the opposite ends of the expander terminating in outwardly curved portions each having an opening, and tension members having ends provided with hooks for insertion into the openings at the opposite ends, for maintaining the expander in contracted position so that it may be easily inserted into a piston skirt, the tension members being readily detachable from the expanderwhile in the skirt to permit the expander to extend into expanded operativeengagement therewith.

3. A spring metal expander for the skirt of a piston, the expander comprising two complementary members, each of which has a central portion provided with an opening for a piston pin I and adapted to contact with a piston pin boss, the

ends being each provided with curved expansible formations comprising'a section inwardly concave on a comparatively large radius of curvature and an outer section outwardly concave on a smaller curvature, each end of each member having an inwardly extending tongue, and means for interconnecting the opposed tongues to retain the two members in assembled position whereby an expander of generally oval shape is formed.

MARTIN E. SIPE. 

